Low-voltage battery charging system and method

Abstract

This application relates to the technical field of electric vehicles, and in particular, to charging systems and methods. An example charging system includes: a low-voltage battery capable of supplying power to a low-voltage electrical device of a vehicle; a power battery module; a direct current-to-direct current (DC-DC) converter capable of receiving a voltage supplied by the power battery module in response to at least that a positive relay and a negative relay of the power battery module are closed, and converting the voltage into a charging voltage of the low-voltage battery to charge the low-voltage battery; and a DC-DC controller electrically connected to the low-voltage battery and capable of monitoring a voltage of the low-voltage battery in response to at least that the vehicle is in a dormant state.

What is claimed is: 
     
       1. A charging system, configured in a vehicle, wherein the charging system comprises:
 a low-voltage battery capable of supplying power to a low-voltage electrical device of the vehicle; 
 a power battery module comprising a plurality of power batteries connected in series; 
 a direct current-to-direct current (DC-DC) converter capable of receiving a voltage supplied by the power battery module in response to at least that a positive relay and a negative relay of the power battery module are closed, and converting the voltage into a charging voltage of the low-voltage battery to charge the low-voltage battery, wherein the power battery module and the DC-DC converter are housed in a same high-voltage protective enclosure; and 
 a DC-DC controller electrically connected to the low-voltage battery and capable of monitoring a voltage of the low-voltage battery in response to at least that the vehicle is in a dormant state, wherein: 
 the DC-DC controller is communicatively connected to a battery management system (BMS) of the vehicle, to wake up the BMS in response to at least that the voltage of the low-voltage battery is lower than a first threshold and to cause the BMS to close the positive relay and the negative relay, wherein a first power battery in the plurality of power batteries is configured to supply power to the low-voltage electrical device of the vehicle in response to at least that the voltage of the low-voltage battery is lower than a third threshold; 
 the DC-DC controller is communicatively connected to a vehicle control unit of the vehicle, to wake up the vehicle control unit in response to at least that the voltage of the low-voltage battery is lower than the first threshold; 
 the vehicle control unit is configured to: monitor a state of the vehicle, and in response to at least that the state of the vehicle meets a high-voltage power-on condition, send a high-voltage power-on instruction to the BMS; 
 the BMS closes the positive relay and the negative relay in response to the high-voltage power-on instruction; 
 the high-voltage power-on condition is that the DC-DC converter is not faulty, the power battery module is not faulty, and a state of charge (SOC) of the power battery module is higher than a second threshold; and 
 the DC-DC controller is electrically connected to the DC-DC converter to monitor whether the DC-DC converter becomes faulty. 
 
     
     
       2. The charging system according to  claim 1 , wherein the power battery module is composed of the plurality of power batteries connected in series. 
     
     
       3. The charging system according to  claim 2 , wherein the first power battery is composed of K batteries in the plurality of power batteries connected in series, and a maximum output voltage of the first power battery is less than or equal to a maximum withstand voltage of the low-voltage electrical device, wherein K≥1, and K is an integer. 
     
     
       4. The charging system according to  claim 3 , wherein an electrical switch is disposed between the first power battery and the low-voltage electrical device of the vehicle, wherein in response to at least that the voltage of the low-voltage battery is lower than the first threshold, the electrical switch is closed to cause the first power battery to supply power to the low-voltage electrical device of the vehicle. 
     
     
       5. The charging system according to  claim 4 , wherein the DC-DC controller is further configured to: in response to at least that the low-voltage battery is charged, monitor the voltage of the low-voltage battery, to monitor whether a fault occurs in charging of the low-voltage battery. 
     
     
       6. The charging system according to  claim 1 , wherein one of the plurality of power batteries is a lithium-ion battery comprising lithium-ion battery cells connected in series. 
     
     
       7. The charging system according to  claim 1 , wherein the DC-DC controller is configured to: in response to at least that the low-voltage battery is charged, send charging stop information to the BMS. 
     
     
       8. The charging system according to  claim 7 , wherein the BMS is configured to: in response to the charging stop information, open the positive relay and the negative relay. 
     
     
       9. A vehicle, comprising a charging system, wherein the charging system comprises:
 a low-voltage battery capable of supplying power to a low-voltage electrical device of the vehicle; 
 a power battery module comprising a plurality of power batteries connected in series; 
 a direct current-to-direct current (DC-DC) converter capable of receiving a voltage supplied by the power battery module in response to at least that a positive relay and a negative relay of the power battery module are closed, and converting the voltage into a charging voltage of the low-voltage battery to charge the low-voltage battery, wherein the power battery module and the DC-DC converter are housed in a same high-voltage protective enclosure; and 
 a DC-DC controller electrically connected to the low-voltage battery and capable of monitoring a voltage of the low-voltage battery in response to at least that the vehicle is in a dormant state, wherein: 
 the DC-DC controller is communicatively connected to a battery management system (BMS) of the vehicle, to wake up the BMS in response to at least that the voltage of the low-voltage battery is lower than a first threshold and to cause the BMS to close the positive relay and the negative relay, wherein a first power battery in the plurality of power batteries is configured to supply power to the low-voltage electrical device of the vehicle in response to at least that the voltage of the low-voltage battery is lower than a third threshold; 
 the DC-DC controller is communicatively connected to a vehicle control unit of the vehicle, to wake up the vehicle control unit in response to at least that the voltage of the low-voltage battery is lower than the first threshold; 
 the vehicle control unit is configured to: monitor a state of the vehicle, and in response to at least that the state of the vehicle meets a high-voltage power-on condition, send a high-voltage power-on instruction to the BMS; 
 the BMS closes the positive relay and the negative relay in response to the high-voltage power-on instruction; 
 the high-voltage power-on condition is that the DC-DC converter is not faulty, the power battery module is not faulty, and a state of charge (SOC) of the power battery module is higher than a second threshold; and 
 the DC-DC controller is electrically connected to the DC-DC converter to monitor whether the DC-DC converter becomes faulty. 
 
     
     
       10. A method for low voltage battery charging, applied to a charging system in a vehicle, wherein the charging system comprises a low-voltage battery, a power battery module comprising a plurality of power batteries connected in series, a direct current-to-direct current (DC-DC) converter, and a DC-DC controller; and the method comprises:
 monitoring, by the DC-DC controller, a voltage of the low-voltage battery in response to at least that the vehicle is in a dormant state; 
 waking up, by the DC-DC controller, a battery management system (BMS) of the vehicle in response to at least that the voltage of the low-voltage battery is lower than a first threshold to cause the BMS to close a positive relay and a negative relay of the power battery module, and the power battery module charges the low-voltage battery via the DC-DC converter, wherein the power battery module and the DC-DC converter are housed in a same high-voltage protective enclosure; 
 controlling, by the DC-DC controller, a first power battery in the plurality of power batteries to supply power to a low-voltage electrical device of the vehicle in response to at least that the voltage of the low-voltage battery is lower than a third threshold; 
 waking up, by the DC-DC controller, a vehicle control unit of the vehicle to cause the vehicle control unit to send a high-voltage power-on instruction to the BMS in response to at least that the vehicle meets a high-voltage power-on condition, wherein the high-voltage power-on condition is that the DC-DC converter is not faulty, the power battery module is not faulty, and a state of charge (SOC) of the power battery module is higher than a second threshold; 
 closing, by the BMS, the positive relay and the negative relay in response to the high-voltage power-on instruction; 
 monitoring, by the DC-DC controller, the SOC of the low-voltage battery in response to at least that the low-voltage battery is in a charging state; and 
 in response to at least that the SOC of the low-voltage battery is greater than or equal to a preset charging stop threshold, sending, by the DC-DC controller, charging stop information to the BMS to cause the BMS to open the positive relay and the negative relay. 
 
     
     
       11. The method according to  claim 10 , wherein
 the power battery module is composed of the plurality of power batteries connected in series; and 
 the first power battery is composed of K batteries in the plurality of power batteries connected in series, and a maximum output voltage of the first power battery is less than or equal to a maximum withstand voltage of the low-voltage electrical device, wherein K≥1, and K is an integer; and the third threshold is lower than the first threshold. 
 
     
     
       12. The vehicle according to  claim 9 , wherein the power battery module is composed of the plurality of power batteries connected in series. 
     
     
       13. The vehicle according to  claim 12 , wherein the first power battery is composed of K batteries in the plurality of power batteries connected in series, and a maximum output voltage of the first power battery is less than or equal to a maximum withstand voltage of the low-voltage electrical device, wherein K≥1, and K is an integer. 
     
     
       14. The vehicle according to  claim 13 , wherein an electrical switch is disposed between the first power battery and the low-voltage electrical device of the vehicle, wherein in response to at least that the voltage of the low-voltage battery is lower than the first threshold, the electrical switch is closed to cause the first power battery to supply power to the low-voltage electrical device of the vehicle. 
     
     
       15. The vehicle according to  claim 9 , wherein one of the plurality of power batteries is a lithium-ion battery comprising lithium-ion battery cells connected in series. 
     
     
       16. The vehicle according to  claim 9 , wherein the DC-DC controller is configured to: in response to at least that the low-voltage battery is charged, send charging stop information to the BMS. 
     
     
       17. The vehicle according to  claim 16 , wherein the BMS is configured to: in response to the charging stop information, open the positive relay and the negative relay. 
     
     
       18. The method according to  claim 10 , wherein one of the plurality of power batteries is a lithium-ion battery comprising lithium-ion battery cells connected in series. 
     
     
       19. The method according to  claim 10 , further comprising:
 sending, by the DC-DC controller, charging stop information to the BMS in response to at least that the low-voltage battery is charged. 
 
     
     
       20. The method according to  claim 19 , further comprising:
 opening, by the BMS, the positive relay and the negative relay in response to the charging stop information.